ABSTRACT Support is requested for a Keystone Symposia conference entitled HIV Vaccines, organized by Drs. Persephone Borrow, Georgia D. Tomaras and Rogier W. Sanders. The conference will be held in Keystone, Colorado from March 22-26, 2020. Development of effective prophylactic human immunodeficiency virus (HIV) vaccines are still urgently needed to halt the spread of the HIV/AIDS pandemic. However, development of these vaccines has proven to be a challenge that, despite intensive research efforts over the last 30 years, science has failed to surmount. Nevertheless, the prospects for an effective HIV vaccine have recently been transformed by a series of advances in science. These advances suggest that induction of broadly-reactive antibodies that confer protection via neutralization and/or neutralization-independent mechanisms and elicitation of cytotoxic (CD8) T cell responses can potentially eradicate the virus early after transmission and may ultimately prove to be achievable goals for drug development. This conference will bring together interdisciplinary investigators whose complementary expertise will synergize to inform HIV vaccine design and evaluation to discuss progress and outstanding challenges in areas such as: 1) The design of immunogens and strategies for optimization of germinal center responses to elicit HIV-1 broadly neutralizing antibodies; 2) Identifying prospects for harnessing other antibody effector functions to confer protection; 3) Developing approaches for eliciting rapidly-acting, efficacious HIV-specific CD8 T cell responses; and 4) How to use novel technologies, animal model systems and small-scale clinical trials to inform vaccine development efforts. This conference is being held jointly with HIV Pathogenesis and Cure. This pairing will provide an opportunity for interaction between investigators working in these related areas, and for joint discussion of therapeutic vaccination strategies.